Gear capable of being flanged onto an electric motor

ABSTRACT

In a gear which can be flanged onto an electric motor, especially a low-clearance planetary gear, with a hollow shaft to make a positive connection with the electric motor output shaft, an easily manufactured and reliable centering system is to be provided between the gear and the electric motor (6). To this end, the section of the hollow shaft (9) accepting the output shaft (10) of the electric motor is centrically secured on roller bearings (11) and the face of the drive flange is radially freely centerable (7, 8) in relation to the mating surface of the electric motor. To enable a drive with as uniform a basic structure as possible to be connected to electric motors with different connecting geometries, the gear has an interchangeable mating plate (2) forming its connecting flange and a hollow shaft into which compensating sleeves (12) can be inserted to accept electric motor output shafts of different diameters.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a gear flanged onto an electric.

2. The Prior Art

In hitherto known gears of this type, in the case of direct flanging theelectric motor is in each case centered radially on the gear flange, forwhich purpose a centering collar mounted in one of the two parts engageswith an exact fit into a corresponding inner centering of the otherpart.

In centering of this type, if manufacturing tolerances of the centeringsurfaces meet in an unfavorable manner a distorted mounting of theelectric motor output shaft relative to the hollow shaft receiving thismay occur. Moreover, the production of the respective centering surfacesinvolves a high outlay in terms of manufacture.

Furthermore, it is known from EP 0,381,829 A1 to flange the electricmotor onto the gear via an elastic multipart connecting element and toprovide radially centering-free bearing surfaces within the individualparts of this element. This mode of connection is complicated in termsof construction and leads to an increase, undesirable per se, in theoverall length of the structural unit consisting of the motor andflanged-on gear.

SUMMARY OF THE INVENTION

The problem with which the invention is primarily concerned is toprovide an improvement and a simplification in construction andmanufacture here.

The design according to the present invention constitutes a solution tothis.

This solution is based on the idea of bringing about the radialcentering solely by means of the connection between the electric motoroutput shaft and the gear hollow shaft receiving this. For this purpose,the hollow shaft is mounted in an appropriately exact and stable mannerwithin the gear case via a rolling bearing attached to the receptionregion. A design of the hollow shaft for the non-positive reception ofthe motor output shaft is especially advantageous.

Furthermore, such a gear is to be connectable, in a basic designremaining unchanged, to electric motors having different connectinggeometries, that is to say different output shaft diameters and flangedesigns.

The absence of radial centering between the flange and electric motorhousing is especially advantageous in the design according to thepresent invention. For, in this case, altogether four centering surfacesare dispensed with, since, in the case of a centered connection, such acompensating plate would have to be centered, on each of its end faces,relative to the respective bearing surface, that is to say the gearcase, on the one hand, and relative to the electric motor housing, onthe other hand.

When a compensating plate with only plane end faces as bearing surfacesis used, it can be produced simply and with great accuracy as regardsthe parallelism of its end faces. It is substantially more complicatedand more costly if this plate had to be manufactured not onlyplane-parallel, but additionally also with radial centering surfaces.For to achieve this, the plate would have to be rechucked to allowdifferent machining tools to be used. Also, in comparison with an onlyplane-parallel plate, additional outlay in terms of measurement would benecessary for the manufacturing inspection.

By means of the compensating sleeve provided according to claim 7, anidentical basic gear case can be flanged onto electric motors havingdifferent output shaft diameters simply by the provision ofcorrespondingly adapted compensating sleeves.

With the present invention an extremely efficient supply of gears forelectric motors having different connecting geometries is possible.

As a result, the compensating plate has the same thickness in all cases.Such a compensating plate is adapted circumferentially to the respectivedifferent geometries of the electric motor output flange. This ispossible in a very simple way without any variation in the basic geardesign. Recesses matched to the individual mounting situation can alsobe worked in the motor-side bearing surface of the compensating platefor the purpose of a radially non-centered reception of a centeringcollar present on the output flange of the electric motor for otherinstallation purposes.

In the basic gear design, the dimensions of the hollow shaft taking theform of a plug-in sleeve are such that, both in terms of length and interms of diameter, it can receive virtually any motor shaft of electricmotors usually capable of being flanged onto such gears. In terms oflength, this presents no problem, since the reception length is merelyto be designed for any predeterminable maximum length of a motor outputshaft which is just still receivable. Shorter shafts then simply fillthe reception region only partially in terms of length.

In terms of diameter, however, special compensating measures must betaken. This is done by the proposed use of compensating sleeves in thecase of a basic hollow-shaft bore designed for the reception of a shafthaving any predetermined maximum outside diameter. The basic gear canconsequently be directly flanged, simply by the use of differentcompensating sleeves, onto electric motors having shaft diameters whichare of any size within a predetermined range. In contrast to the hollowshaft, the compensating sleeves can be produced simply and thereforealso in small quantities cost-effectively. They can either be kept instock in a multiplicity of alternative designs or be produced in eachindividual case for a specific instance of use for an already existingbasic gear, especially one kept in stock. The same applies to thecompensating plates according to the invention.

Consequently, identical basic gear cases can be produced in largequantities and therefore cost-effectively and be adapted to theparticular actual instances of use merely by means of differentcompensating plates and compensating sleeves.

Even the gear length can be varied extremely efficiently merely by asimple change in thickness of the compensating plate and an exchange ofthe hollow shaft, with the basic gear design otherwise remaining thesame.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is represented in the drawing.

In this:

FIG. 1 shows a longitudinal section through the connection region of aplanetary gear flanged onto an electric motor,

FIG. 2 shows a section along the line II--II through the plug-in sleeveportion of a gear hollow shaft receiving the output shaft of theelectric motor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The case 1 of a planetary gear 100 is flanged onto an electric motor 6via gear flange in the form of a compensating plate 2. At the same time,the compensating plate 2 is connected, on the one hand, to the gear case1 via screws 3 and, on the other hand, to the housing of the electricmotor 6 via screws 4.

The compensating plate 2 has a bearing surface 19 that bears simply flatagainst the respective bearing surface 20 of the electric motor 6. Thereis no radial centering of the compensating plate 2 relative to theoutput flange 5 of the electric motor 6. In order to avoid this in anoutput flange 5 of an electric motor 6, said output flange having acentering collar 7, a recess 8 is worked into the compensating plate 2on the motor side. The compensating plate 2 has a bearing surface 18that also bears merely flat against the case 1 of the planetary gear andis exchangeable relative to this. The compensating plate 2 can beexchanged so that different mounting geometries of diverse electricmotors 6 can be compensated. The different compensating plates 2necessary for this purpose have in each instance only different outerdimensions, with the width, that is to say thickness, otherwiseremaining basically the same.

The outer contour of a compensating plate can consequently easily beadapted in each instance to the corresponding contour of the motoroutput flange 5. The provision of a recess 8, described further above,for the radially centering-free reception of an electric motor outputflange 5 having a centering collar 7 present on the latter for othermounting purposes can also be ensured simply in this way.

The radial centering between the planetary gear case 1 and the electricmotor 6 is produced solely via the output shaft 10 of the electric motor6, said output shaft engaging into a hollow driveshaft 9 of theplanetary gear. For this purpose, the hollow shaft 9 is mounted in acentrically stable manner in the case 1 of the planetary gear via arolling bearing 11 in the reception region 15 of the output shaft 10.The hollow shaft 9 itself is designed as a clampable, radially slottedplug-in sleeve, so that the output shaft 10 can be receivednon-positively with an exact fit.

So that a basic gear case with a hollow shaft 9 which is the same ineach instance can be connected to electric motors 6 having output shafts10 with different diameters, radially slotted compensating sleeves 12 ofdiffering thickness can be used.

Thus, for electric motors 6 having different output geometries,identical basic gear cases, in each instance with only differentcompensating plates 2 and/or compensating sleeves 12, can be employed.Highly efficient production and stockkeeping are thereby possible.

We claim:
 1. A low play planetary gears comprising:a gear case flangedonto an electric motor having an output shaft and a bearing surface; ahollow shaft having a reception region for non-positive reception of theoutput shaft; rolling bearings arranged around the reception region formounting the hollow shaft in a centrically fixed manner in the gearcase; and a gear flange connected to the gear case and having a bearingsurface rigidly connected in a radially centering free manner to thebearing surface of the electric motor.
 2. The gear according to claim 1,wherein the hollow shaft is a radially slotted plug-in sleeve for aclamping connection between the hollow shaft and the output shaft. 3.The gear according to claim 1, wherein the gear flange is a compensatingplate exchangeably fastened in a radially centering-free manner to thegear case and having bearing surfaces located plane-parallel oneanother.
 4. The gear according to claim 1, further comprising a radiallyslotted compensating sleeve inserted into the hollow shaft when anelectric motor with an output shaft having a diameter smaller than thatof the hollow shaft is connected.